The first large scale U.S. “clean coal” facility was declared operational — by the large energy firm NRG Energy and JX Nippon Oil & Gas Exploration Corp. Their Petra Nova project, not far outside of Houston, captured carbon dioxide from the process of coal combustion for the first time in September, and has now piped 100,000 tons of it from the plant to the West Ranch oil field 80 miles away, where the carbon dioxide is used to force additional oil from the ground. The companies say that the plant can capture over 90 percent of the carbon dioxide released from the equivalent of a 240 megawatt, or million watt, coal unit, which translates into 5,000 tons of carbon dioxide per day or over 1 million tons per year. They’re calling it “the world’s largest post-combustion carbon capture system.”